Substrates coated with mixtures of titanium and aluminum materials, methods for making the substrates, and cathode targets of titanium and aluminum metal

ABSTRACT

Titanium and aluminum cathode targets are disclosed for sputtering absorbing coatings of titanium and aluminum-containing materials in atmospheres comprising inert gas, reactive gases such as nitrogen, oxygen, and mixtures thereof, which can further comprise inert gas, such as argon, to form nitrides, oxides, and oxynitrides, as well as metallic films. The titanium and aluminum-containing coatings can be utilized as an outer coat or as one or more coating layers of a coating stack.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 60/458,819 filed Mar. 28, 2003, which is herein incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to coatings comprising titaniumand aluminum on substrates, methods for coating such mixtures, andtitanium and aluminum-containing materials as sputtering targets.

2. Description of Technical Considerations

Technology for depositing specific types of metallic or metaloxide-containing coatings on larger area substrates includes variousmethods, such as vapor deposition, like chemical vapor deposition; spraypyrolysis; sol-gel; and sputtering, such as magnetic sputtering vapordeposition (“MSVD”). Larger area substrates of around 1 square foot (30square centimeters) and larger provide challenges in economicallyconsistent production of quality coated substrates by virtue of the sizeof the substrate that is coated. Consistency in coating uniformity andreduction of defects in the coating of larger areas require equipmentthat is able to handle the larger substrates and the volumes of coatingmaterial and the fabrication of the coated substrate. Such equipment isgenerally more expensive to purchase and operate; thus making efficientoperation of the equipment imperative for cost-effective production.

Specific metallic (metals and/or metal oxide) containing coatings onsubstrates can exist as multi-layered coatings in which each layer iscomprised of the same or different materials from one or moreapplications of the coating materials or precursors. Also, a layer ofthe coating can have one or more films from more than one application ofthe same or different materials. Examples of multi-layered coatings on asubstrate are conventional silver-based low emissivity coatings that aredeposited on both glass and plastic substrates, generally by sputtering.

In sputtering to deposit metals and metal oxides on larger surface areasubstrates, like sheets or panels of light transmitting materials, likeplastic or glass, cathode targets have been used of the specific metalfor deposition as the metal or metal oxide on the substrate. For largerarea substrates of plastic and glass, such as float glass with a surfacearea of at least 1 square foot (30 square centimeters), elongatedcathode targets have been used. The targets are elongated to a lengthsubstantially the length or width of the substrate to be coated. Forexample, U.S. Pat. Nos. 4,990,234 and 5,170,291 to Szczyrbowski et al.and U.S. Pat. No. 5,417,827 to Finley disclose sputtering silica andsilicides, such as transition metal silicide (NiSi₂), in an oxidizingatmosphere to deposit dielectric oxide films.

U.S. Pat. No. 5,320,729 to Narizuka et al. discloses a sputtering targetwith which a high resistivity thin film consisting of silicon, titaniumand aluminum, and oxygen can be produced. The target is formed byselecting the grain size of silicon powder and titanium and aluminumdioxide powder drying the powders by heating and mixing the driedpowders to obtain a mixed powder containing from 20 to 80 percent byweight of silicon, for example 50 to 80 percent, the remainder beingtitanium and aluminum dioxide, packing the mixed powder in a die, andsintering the packed powder by hot pressing to produce a target whichhas a two-phase mixed structure. The sputtering target is used tomanufacture thin film resistors and electrical circuits.

Sputtering cathode targets of various metallic materials are useful invacuum deposited low emissivity (“Low-E”) coating stacks which usuallyhave the following general layer sequence: S/(D₁/M/P/D₂)^(R) where:

-   S is a substrate, such as a transparent substrate like glass;-   D₁ is a first transparent dielectric layer, usually a metal oxide,    and can include one or more transparent dielectric films;-   M is an infrared reflective layer, usually silver or other noble    metal;-   P is a primer layer to protect the underlying infrared reflective    layer;-   D₂ is a second transparent dielectric film similar to D₁; and-   R is an integer equal to or greater than one and is the number of    repetitions of the above layers.

The dielectric layers, D₁ and D₂, adjust the optical properties of thecoating stack. These layers also provide some physical and chemicalprotection to the fragile infrared reflective layer(s). Unfortunately,many process-friendly and cost-effective dielectric materials are oftensusceptible to abrasion and corrosion as well. For example, zinc oxide,e.g., as disclosed in U.S. Pat. No. 5,296,302, which usually forms acrystalline film, is susceptible to attack by acids and bases; bismuthoxide, which usually forms an amorphous film, is soluble in certainacids; tin oxide, which usually forms an amorphous film, is susceptibleto attack in certain basic environments.

The P primer or blocker layers, as they are known in the art, areincorporated into such low emissivity coatings to protect the M layer orfilm from oxidation during the sputtering process. The M layer, likesilver, is susceptible to breakdown during deposition of the overlyingdielectric layer or film if the oxygen to reactive gas ratio is high,e.g., greater than 20 percent of the gas volume. The primer layers,which can be composed of pure metal layers or ceramic layers, act assacrificial layers by preferentially oxidizing to protect the underlyingsilver layer or film. Generally thicker primer layers are necessary ifthe low emissivity coating is to survive the high temperature of a glassfabrication process (up to 650° C. or 1202° F.), e.g., bending andtempering of soda-lime glass.

To reduce corrosion, some Low-E coating stacks have an overlayingprotective overcoat of a chemically-resistant dielectric layer. Thislayer has desirable optical properties, manageable sputter depositioncharacteristics, and is compatible with other materials of the coatingstack. The titanium dioxide films disclosed in U.S. Pat. Nos. 4,716,086and 4,786,563 are protective films having the above qualities. There areother chemically-resistant materials that have limitations, e.g., aremore challenging to sputter. Silicon oxide disclosed in Canadian PatentNo. 2,156,571, aluminum oxide and silicon nitride disclosed in U.S. Pat.Nos. 5,425,861; 5,344,718; 5,376,455; 5,584,902; and 5,532,180, and inPCT International Publication No. WO 95/29883 are examples of suchmaterials. The sputtered multi-layered silver-based low emissivitycoatings and glass with these coatings are used in automotive and windowglazing applications.

It is known that the primer layer continues to oxidize during hightemperature processing, and it is desirable for the oxidation tocontinue to completion in order to reduce visible light absorption fromthe primer layer. This effect is better utilized for metals that formmetal oxides with low absorption coefficients, e.g., titanium andaluminum. For performance glazing applications, this leads to a highervisible light transmission to infrared transmittance ratio. If theoxidation continues beyond consumption of the primer layer to fulloxidation, the coating can degrade and performance can suffer. Metalions in the dielectric layers can inter-diffuse with the silver layer,and the well-defined interface can become fuzzy. This can lead to a lossof the antireflective behavior and loss of a continuous silver layer.The degree of oxidation of the primer is related to several factors,including the reactivity of the metal (Gibbs free energy), the densityof the oxide formed during heating, and the diffusion or dissolution ofoxygen in the oxide or metal. For example, a metal, such as titanium, ina thin film of less than around 20 Angstroms will pass through severaloxidation states before reaching the thermally stable phase of TiO₂.Titanium has been a preferred choice of material for primer layers inlow emissivity multi-layered coatings.

The technology of metal and metallic coatings and multi-layered coatingswould be advanced by a more chemically and/or mechanically durablecoating that could be used as a protective coat for the substrate ormulti-layered coated substrate or also useful as a dielectric or primerlayer in multi-layered coatings on substrates.

SUMMARY OF THE INVENTION

The present invention involves coatings of at least mixtures of titaniumand aluminum-containing materials on flat and/or curved substrates thatcan be larger than at least 1 square foot (30 square centimeters). Inone non-limiting embodiment of the invention, the titanium andaluminum-containing coatings (“Ti—Al coating”) have a weight ratio oftitanium-containing materials to aluminum-containing materials,respectively, in the range of around 99:1 to 1:99 for the mixture oftitanium and aluminum-containing materials (“Ti—Al containingmaterials”), such as 40 to 80 titanium to 20 to 60 aluminum, such as 50to 80 titanium to 20 to 50 aluminum, such as 50 to 70 titanium to 30 to50 aluminum, such as 60 to 70 titanium to 30 to 40 aluminum. Applicationof the Ti—Al containing materials can be via several coating techniqueswell know in the art, such as but not limited to vapor deposition, spraypyrolysis, sol gel and/or sputtering methods. The flat or curvedsubstrates can be, but are not limited to, non-metallic uncoated basesubstrates, plastics, PET, glass, light-transmitting substrates, andalready coated variations of these substrates and the like in the formof flat, curved or contoured substrates.

In one non-limiting embodiment of the present invention, the Ti—Alcoating is deposited by sputtering Ti—Al containing materials fromcathode targets. These targets can be elongated planar or cylindricaltargets comprised of at least titanium and aluminum mixtures or alloys.The targets can also have other materials, such as transition metals,like silicon, silicon-transition metal, or transition metal and/orsilicon. The targets can also have other materials to affect theconductivity of the cathode target. Targets of titanium and aluminummixtures can be sputtered in an atmosphere comprising inert gas,nitrogen, oxygen, and/or mixtures thereof to produce titanium andaluminum metal-containing coatings including oxides, nitrides andoxynitrides, as well as metallic films on substrates. The titanium andaluminum metal cathode target compositions of the present inventioncomprise sufficient metal to provide target stability and a desirablesputtering rate.

The titanium and aluminum-containing targets, which as oxides, nitridesand/or oxynitrides materials are very hard and chemically resistant,produce sputtered mechanically and/or chemically durable titanium andaluminum mixture or alloy compound coatings. When the Ti—Al mixtures aresputtered in pure argon, or in an oxygen and argon gas mixture, theresultant titanium and aluminum mixture coating is more chemicallyresistant than titanium and aluminum alone and harder than titaniumoxide alone.

A purpose of these titanium and aluminum mixtures is to provide targetmaterials that sputter readily in inert gas, reactive gas or gasmixtures, to produce extremely durable coatings with variable opticalproperties. Each target material combination can produce coatings withdifferent optical constants, i.e., refractive index and absorptioncoefficient. When sputtered reactively, each target material combinationcan also produce coatings with a range of optical constants, whichgenerally increase as the reactive gas mixture, with or without inertgas, such as argon, is varied from oxygen, to combinations of oxygen andnitrogen with increasing proportions of nitrogen, to nitrogen.

In one embodiment of the present invention, the coatings with Ti—Almixtures permit a widening of the range of the oxidation of the primerlayers and better control of the thermal processing of the lowemissivity coatings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view (not to scale) of a coated articleincorporating features of the invention;

FIG. 2 is a graph of coating composition versus position for a coatedglass plate;

FIG. 3 is a graph of sheet resistance versus weight percent titania fora coated article incorporating features of the invention;

FIGS. 4 and 5 are graphs of reflectance versus time for coated articlesof the invention;

FIG. 6 is a graph of reflectance versus time for a coated article of theinvention;

FIG. 7 is a graph of reflectance versus time for a coated article of theinvention;

FIG. 8 is a graph of thickness versus atomic percent aluminum for acoating of the invention;

FIG. 9 is a graph of sheet resistance versus position for a coated glassplate;

FIG. 10 is a graph of sheet resistance versus weight percent aluminumfor a coated article of the invention;

FIG. 11 is a graph of sheet resistance versus atomic percent titaniumfor a coating of the invention;

FIG. 12 is a graph of sheet resistance versus atomic percent aluminumfor a coating of the invention;

FIGS. 13 and 14 are graphs of sheet resistance versus thickness forcoatings of the invention before and after heating;

FIGS. 15 and 16 are graphs of transmittance versus thickness forcoatings of the invention before and after heating;

FIG. 17 is a graph of percent coating removed versus time for variouscoatings of the invention;

FIG. 18 is a graph of time until 80 percent coating removal versusatomic percent aluminum for a coating of the invention;

FIG. 19 is a graph of percent coating removed versus time for variouscoatings of the invention; and

FIG. 20 is a graph of refractive index and extinction coefficient versusatomic percent aluminum and weight percent aluminum for coatings of theinvention.

DESCRIPTION OF THE INVENTION

As used herein, the terms “coating film” or “film” refer to a region ofa desired or selected coating composition. A “coating layer” or “layer”can include one or more coating films. A “coating stack” or “stack”includes one or more coating layers. As used herein, spatial ordirectional terms, such as “left”, “right”, “inner”, “outer”, “above”,“below”, “top”, “bottom”, and the like, relate to the invention as it isshown in the drawing figures. However, it is to be understood that theinvention can assume various alternative orientations and, accordingly,such terms are not to be considered as limiting. Further, as usedherein, all numbers expressing dimensions, physical characteristics,processing parameters, quantities of ingredients, reaction conditions,and the like, used in the specification and claims are to be understoodas being modified in all instances by the term “about”. Accordingly,unless indicated to the contrary, the numerical values set forth in thefollowing specification and claims can vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical value should atleast be construed in light of the number of reported significant digitsand by applying ordinary rounding techniques. Moreover, all rangesdisclosed herein are to be understood to encompass the beginning andending range values and any and all subranges subsumed therein. Forexample, a stated range of “1 to 10” should be considered to include anyand all subranges between (and inclusive of) the minimum value of 1 andthe maximum value of 10; that is, all subranges beginning with a minimumvalue of 1 or more and ending with a maximum value of 10 or less, e.g.,1 to 7.2, or 3.5 to 6.1, or 5.5 to 10, just to illustrate a few. Theterms “flat” or “substantially flat” substrate refer to a substrate thatis substantially planar in form; that is, a substrate lying primarily ina single geometric plane, which substrate, as would be understood by oneskilled in the art, can include slight bends, projections, ordepressions therein. Further, as used herein, the terms “depositedover”, “applied over”, or “provided over” mean deposited, applied, orprovided on but not necessarily in contact with the surface. Forexample, a coating “deposited over” a substrate does not preclude thepresence of one or more other coating films of the same or differentcomposition located between the deposited coating and the substrate. Forinstance, the substrate itself can include a coating such as those knownin the art for coating substrates, such as glass and ceramics. Allreferences referred to herein are to be understood to be incorporated byreference in their entirety.

The instant invention relates to titanium and aluminum-containing filmsor layers that can be used as dielectric, primer, and/or protectivelayers or films that can protect all or selected ones of the underlyingcoating layers or films of a coating stack from mechanical wear and/orchemical attack. In the following discussion, the embodiments of theinvention can protect underlying infrared reflective metal layers orfilms as part of a functional film or layer and metal oxide layers ofthe type present in any conventional type of coating stack.

The titanium and aluminum-containing films or layers of the presentinvention can be formed or deposited over substrates by various methods,such as but not limited to sol gel, vapor deposition, and sputtering.

For both the CVD and the spray pyrolysis methods of coating the titaniumaluminum materials of the present invention, the temperature of thesubstrate during formation of the coating thereon should be within therange that will cause the metal containing precursor to decompose andform a coating. As should be appreciated, the lower limit of thistemperature range is largely affected by the decomposition temperatureof the selected metal-containing precursor. For the titanium-containingprecursors, like those of U.S. Pat. No .6,027,766 (Greenberg et al.) andothers well known in the art, the minimum temperature of the substratewhich will provide sufficient decomposition of the precursor istypically within the temperature range of 400° C. (752° F.) to 500° C.(932° F.). The upper limit of this temperature range can be affected bythe substrate being coated. For example, where the substrate is a glassfloat ribbon and the coating is applied to the float ribbon duringmanufacture of the float ribbon, the float glass can reach temperaturesin excess of 1000° C. (1832° F.). The float glass ribbon is usuallyattenuated or sized (e.g., stretched or compressed) at temperaturesabove 800° C. (1472° F.). If the coating is applied to the float glassbefore or during attenuation, the coating can crack or crinkle as thefloat ribbon is stretched or compressed, respectively. Therefore, in onepractice of the invention, the coating is applied when the float ribbonis dimensionally stable, e.g., below 800° C. (1472° F.) forsoda-lime-silica glass, and the float ribbon is at a temperature todecompose the metal-containing precursor, e.g., above 400° C. (752° F.).Forming a coating by CVD or spray pyrolysis methods is particularly wellsuited for practice during the manufacture of the glass float ribbon. Ingeneral, a glass float ribbon is manufactured by melting glass batchmaterials in a furnace and delivering the refined molten glass onto abath of molten tin. The molten glass on the bath is pulled across thetin bath as a continuous glass ribbon while it is sized and controllablycooled to form a dimensionally stable glass float ribbon. The floatribbon is removed from the tin bath and moved by conveying rolls througha lehr to anneal the float ribbon. The annealed float ribbon is thenmoved through cutting stations on conveyor rolls where the ribbon is cutinto glass sheets of desired length and width. U.S. Pat. Nos. 4,466,562and 4,671,155 provide a discussion of the float glass process.

Temperatures of the float ribbon on the tin bath generally range from1093° C. (2000° F.) at the delivery end of the bath to 538° C. (1000°F.) at the exit end of the bath. The temperature of the float ribbonbetween the tin bath and the annealing lehr is generally in the range of480° C. (896° F.) to 580° C. (1076° F.); the temperatures of the floatribbon in the annealing lehr generally range from 2040C (400° F.) to557° C. (1035° F.) peak.

U.S. Pat. Nos. 4,853,257; 4,971,843; 5,464,657; and 5,599,387 describeCVD coating apparatus and methods that can be used in the practice ofthe invention to coat the float ribbon during manufacture thereof.Because the CVD method can coat a moving float ribbon yet withstand theharsh environments associated with manufacturing the float ribbon, theCVD method is well suited to provide the coating on the float ribbon.

The CVD coating apparatus can be employed at several points in the floatribbon manufacturing process. For example, CVD coating apparatus can beemployed as the float ribbon travels through the tin bath after it exitsthe tin bath, before it enters the annealing lehr, as it travels throughthe annealing lehr, or after it exits the annealing lehr.

As can be appreciated by those skilled in the art, concentration of themetal-containing precursor in the carrier gas, the rate of flow of thecarrier gas, the speed of the float ribbon (the “line speed”), thesurface area of the CVD coating apparatus relative to the surface areaof the float ribbon, the surface areas and rate of flow of exhaustedcarrier gas through exhaust vents of the CVD coating apparatus, moreparticularly, the ratio of exhaust rate through the exhaust vents versusthe carrier gas input rate through the CVD coating unit, known as the“exhaust matching ratio”, and the temperature of the float ribbon areamong the parameters which will affect the final thickness andmorphology of the coating formed on float ribbon by the CVD process.

U.S. Pat. Nos. 4,719,126; 4,719,127; 4,111,150; and 3,660,061 describespray pyrolysis apparatus and methods that can be used with the floatribbon manufacturing process. While the spray pyrolysis method, like theCVD method, is well suited for coating a moving float glass ribbon, thespray pyrolysis has more complex equipment than the CVD equipment and isusually employed between the exit end of the tin bath and the entranceend of the annealing lehr.

As can be appreciated by those skilled in the art, the constituents andconcentration of the pyrolytically-sprayed aqueous suspension, the linespeed of the float ribbon, the number of pyrolytic spray guns, the spraypressure or volume, the spray pattern, and the temperature of the floatribbon at the time of deposition are among the parameters which willaffect the final thickness and morphology of the coating formed on thefloat ribbon by spray pyrolysis.

As is known by those skilled in the art, the surface of the glass floatribbon on the molten tin (commonly referred to as the “tin side”) hasdiffused tin in the surface which provides the tin side with a patternof tin absorption that is different from the opposing surface not incontact with the molten tin (commonly referred to as “the air side”).This characteristic is discussed in Chemical Characteristics of FloatGlass Surfaces, Seiger, J., JOURNAL OF NON-CRYSTALLINE SOLIDS, Vol. 19,pp. 213-220 (1975); Penetration of Tin in The Bottom Surface of FloatGlass: A Synthesis, Columbin L. et al., JOURNAL OF NON-CRYSTALLINESOLIDS, Vol. 38 & 39, pp. 551-556 (1980); and Tin Oxidation State, DepthProfiles of S-i 2+—and SnA-+ and oxygen Diffusivity in Float Glass byMössbauer Spectroscop, Williams, K. F. E. et al., JOURNAL OFNON-CRYSTALLINE SOLIDS, Vol. 211, pp. 164-172 (1997). As can beappreciated by those skilled in the art, a coating can be formed on theair side of the float ribbon while it is supported on the tin bath (bythe CVD method); on the air side of the float ribbon after it leaves thetin bath by either the CVD or spray pyrolysis methods, and on the tinside of the float ribbon after it exits the tin bath by the CVD method.

U.S. Pat. Nos. 4,379,040; 4,861,669; 4,900,633; 4,920,006; 4,938,857;5,328,768; and 5,492,750 describe MSVD apparatus and methods to sputtercoat metal oxide films on a substrate, including a glass substrate. TheMSVD process is not generally compatible with providing a coating over aglass float ribbon during its manufacture because, among other things,the MSVD process requires negative pressure during the sputteringoperation, which is difficult to form over a continuous moving floatribbon. However, the MSVD method is acceptable to deposit the coatingover the substrate, e.g., a glass sheet. As can be appreciated by thoseskilled in the art, the substrate can be heated to temperatures in therange of 400° C. (750° F.) to 500° C. (932° F.) so that the MSVDsputtered coating on the substrate crystallizes during depositionprocess, thereby eliminating a subsequent heating operation.

The coated substrate can be heated during the sputtering operation. Thesputter coating can be crystallized within the MSVD coating apparatusdirectly and without post heat treatment by using high energy plasmaand/or ion bombardment.

One method to provide a coating using the MSVD method is to sputter acoating on the substrate, remove the coated substrate from the MSVDcoater and thereafter heat treat or treat by using atmospheric plasmason the coated substrate to crystallize the sputter coating. For example,but not limiting to the invention, with the MSVD method, a target oftitanium metal and aluminum metal sputtered in an argon/oxygenatmosphere having 40 to 100% oxygen, the remainder argon gas mixture,for example 50 to 80 percent oxygen, the remainder argon gas mixture, ata pressure of 5-10 millitorr to sputter deposit a coating of titaniumaluminum oxide at the desired thickness on the substrate. The coating asdeposited may not be crystallized. The coated substrate can be removedfrom the coater and heated to a temperature in the range of 400° C.(752° F.) to 600° C. (1112° F.) for a time period sufficient to promoteformation of the crystalline forms of titanium aluminum oxide andmixtures and oxide compounds of titanium and aluminum. Where thesubstrate is a glass sheet cut from a glass float ribbon, the coatingcan be sputter deposited on the air side and/or the tin side.

In one aspect of the present invention, oxides, nitrides, andoxynitrides comprising titanium and aluminum, titanium andaluminum-silicon, titanium and aluminum-silicon-transition metal can besputtered using dc magnetron sputtering. For this purpose, titanium andaluminum, with or without other materials such as silicon or transitionmetals, can be used for the sputtering targets. Coating transmittanceand reflectance are measured as an indicator of the optical propertiesof refractive index and absorption coefficient. Electrical sheetresistance in ohms per square is measured as an indicator of theemissivity and the solar performance, i.e., the solar energy transmittedand reflected. A decrease in sheet resistance indicates an enhancementin these properties.

In one non-limiting embodiment of the invention, titanium and aluminumand titanium aluminum-silicon mixture or alloy cathode targets can havea weight ratio of titanium-containing materials to aluminum-containingmaterials ranging between 1 to 99 weight percent aluminum and 99 to 1weight percent titanium, for example 10 to 95 weight percent aluminum,or 20 to 80 weight percent aluminum, or 20 to 60 weight percentaluminum, such as 20 to 50 weight percent aluminum, such as 20 to 40weight percent aluminum, such as 30 to 40 weight percent aluminum. Themetals of titanium, aluminum with or without silicon can be sputtered inargon, nitrogen, and/or oxygen; for example in an argon-oxygen gasmixture with up to 100 percent oxygen, or in a nitrogen-oxygen gasmixture containing up to 95 percent oxygen. Titanium-aluminum-siliconalloy cathode targets can have some of the silicon substituted withtransition metal. In one non-limiting embodiment if the invention, theamount of transition metal is below 15 percent by weight based on thecombined weight of titanium and aluminum, silicon and transition metal,for example in the range of 5 to 15 percent, with at least 5 percentsilicon based on the total weight of titanium and aluminum, silicon andtransition metal.

Titanium and aluminum-silicon-transition metal alloy cathode targetswith 5 to 15 weight percent transition metal and 5 to 65 weight percentsilicon, for example 5 to 10 weight percent transition metal, and 5 to40 weight percent silicon, can be sputtered, for example, in inert gassuch as argon, in 100% oxygen, in argon-oxygen gas mixtures, or innitrogen-oxygen gas mixtures containing up to 95 percent oxygen. In onenon-limiting embodiment of the invention, titanium andaluminum-transition metal alloy cathode targets can contain up to 20weight percent transition metal based on the combined weight of titaniumand aluminum, but can contain more transition metal or other transitionmetal subject to the limitation that the alloy remain nonmagnetic formagnetron sputtering.

The titanium and aluminum, titanium aluminum-silicon,titanium-aluminum-silicon-transition metal, and titanium andaluminum-transition metal cathode target compositions of the presentinvention can be determined by chemical analysis from pieces of targetmaterial to determine weight percent of silicon, or transition metal.The coating compositions can be measured using X-ray fluorescence todetermine the weight percent titanium, aluminum, silicon, or transitionmetal.

The targets can be generally elongated having a length larger than theirwidth and ranging from 30 up to 100 centimeters or more. In oneembodiment of the present invention, coatings can be produced on alarge-scale magnetron sputtering device capable of coating glass up to100×144 inches (2.54×3.66 meters).

The article having at least one film or layer of titanium and aluminummaterials of the present invention in a coating can be an article havinga sputtered Low-E coating stack on a substrate. The titanium andaluminum material containing coating can be a protective layer over thecoating stack. The substrate can be made of any material, e.g., plastic,glass, metal or ceramic. In one non-limiting embodiment of theinvention, the substrate is transparent, e.g., nylon, glass or Mylar®plastic sheet. In the following discussion, the substrate is glass. Theglass can be of any composition having any optical properties, e.g., anyvalue of visible transmittance, ultraviolet transmission, infraredtransmission and/or total solar energy transmission. Types of glassesthat can be used in the practice of the invention, but not limitedthereto, are disclosed in U.S. Pat. Nos. 4,746,347; 4,792,536;5,240,886; 5,385,872; and 5,393,593.

The sputtered coating stack can have any arrangement including, but isnot limited to, a base layer also referred to as a dielectric layer, aphase matching layer or an antireflective layer; an infrared reflectingmetal layer, such as a silver film or any noble metal; a primer orprotective layer, which can be, but is not limited to, a depositedstainless steel film, a niobium film, a deposited copper film or adeposited titanium film, and a second dielectric layer or antireflectivelayer. Coating stacks that are single silver film coating stacks thatcan be used in the practice of the invention, but not limiting to theinvention, are disclosed in U.S. Pat. Nos. 4,320,155; 4,512,863;4,594,137; and 4,610,771.

For one specific coated glass, the dielectric layers can have zincstannate; the primer layer can be deposited as metallic copper, and theIR layer can be silver. Although not required, the base layer can bedeposited on the air surface of a glass sheet cut from a float glassribbon. The air surface is the surface opposite the surface of the floatribbon supported on the molten pool of metal, e.g., as disclosed in U.S.Pat. No. 4,055,407. An exemplary coating stack as described above isdisclosed in the above-mentioned U.S. Pat. Nos. 4,610,771 and 4,786,563.

The titanium and aluminum-containing layer, e.g., protective layer, ofthe instant invention is discussed below in combination with onenon-limiting configuration of a functional coating stack, but it shouldbe appreciated that the protective layer can be used with many differenttypes of functional coatings known to those skilled in the art.

With reference to FIG. 1, there is shown a coated article 40 having afunctional coating stack 42 of a type typically found in Low E sputtercoated articles having two infrared reflective metal layers. The coatingstack 42 is carried on a substrate 14. In general, the coating stack 42includes a base layer 44 that can include one or more films of differentdielectric materials or antireflective materials or phase matchingmaterials, a first infrared reflective metal layer 46, a primer layer 48to prevent degradation of the metal layer 46 during sputtering of adielectric layer or anti-reflective layer or phase matching layer 50.The layer 50 can have one or more films. A second infrared reflectivemetal layer 52 is deposited over the layer 50. A second primer layer 54is deposited on the second infrared metal reflective layer 52 and adielectric layer or anti-reflective layer 56 is deposited over thesecond primer layer 54.

In one non-limiting embodiment of the invention and with continuedreference to FIG. 1, a double metal layer reflective coating stack 42that can be used in the practice of the invention includes a base layer44 comprising a zinc-stannate film 58 on the air surface of a glasssubstrate 14 cut from a float glass ribbon, and a zinc-oxide film 60 onthe zinc-stannate film 58; a first infrared-reflective metal layer 46comprising a silver film on the zinc oxide film 60; a first primer layer48 comprising a sputtered titanium metal film on the silver film 46,wherein the titanium metal oxidizes to titanium dioxide film 48 duringsputtering of the next dielectric film; a dielectric layer 50 comprisinga zinc-oxide film 62 on the primer layer 48, a zinc-stannate film 64 onthe zinc-oxide film 62, and a zinc-oxide film 66 on the zinc-stannatefilm 64; a second infrared-reflective layer 52 comprising a secondsilver film on the zinc-oxide film 66; a second primer layer 54comprising a second titanium metal film deposited on the silver film 52,wherein the titanium is oxidized to titanium dioxide as previouslydiscussed; a dielectric layer 56 comprising a zinc-oxide film 68 overthe titanium oxide film 54 and a zinc-stannate film 70 on the zinc-oxidefilm 68. The coating stack 42 is of the type disclosed in published EPOApplication No. 0 803 381 based on U.S. patent application Ser. No.08/807,352 filed on Feb. 27, 1997, in the names of Mehran Arbab, RussellC. Criss, and Larry A. Miller for “Coated Articles”, and in productssold by PPG Industries, Inc., under its trademark SUNGATE® 1000 coatedglass and SOLARBAN® 60 coated glass.

The protective layer or film 16 of the instant invention discussed inmore detail below is deposited over the coating stack 42. The depositionof the functional coating 42 is not limiting to the invention and can bedeposited by any method, e.g., by sputter deposition, electroless metaldeposition, and/or pyrolytic deposition. Alternatively, the functionalcoating can comprise one or more conductive metal nitrides, e.g.,titanium nitride, and alloys of nickel and chrome.

It is to be understood that the invention is not limited to theembodiment shown in FIG. 1. For example, the titanium andaluminum-containing layer (e.g., protective layer) of the invention canbe utilized as an overcoat layer 16 as shown in FIG. 1. However, thetitanium and aluminum-containing layer of the invention could also beused as one or both of the primer layers 48 and/or 54, or as anadditional layer, or in place of one or more of the dielectric layers44, 50, 56.

The protective layer 16 of the instant invention can be the lastdeposited layer on the coating stack or can be an underlying layer foroutermost layer. For example, the Ti—Al protective layer 16 of theinstant invention can be deposited as the last film of the functionalcoating to provide protection against mechanical and chemical attack atleast equal to presently known and used protective films. Alternatively,the Ti—Al layer 16 can be utilized as one or more of the layers, e.g.,primer layers or dielectric layers, of the coating stack.

In one non-limiting embodiment of the invention, the protective coating16 further comprises silicon. This can be accomplished by adding siliconto the titanium-aluminum target. When a titanium-aluminum-siliconcathode target is used to sputter a coating in an inert atmosphere, thedeposited material can include titanium, aluminum, silicon,titanium-aluminum, titanium-silicon, aluminum-silicon,titanium-aluminum-silicon, and combinations thereof. When atitanium-aluminum-silicon cathode target is used to sputter a coating inan oxygen atmosphere, the deposited material can include titanium oxide,aluminum oxide, silicon oxide, (titanium-aluminum) oxide,(titanium-silicon) oxide, (aluminum-silicon) oxide,(titanium-aluminum-silicon) oxide, and combinations thereof. When atitanium-aluminum-silicon cathode target is used to sputter a coating innitrogen atmosphere, the deposited material can include titaniumnitride, aluminum nitride, silicon nitride, (titanium-aluminum) nitride,(titanium-silicon) nitride, (aluminum-silicon) nitride,(titanium-aluminum-silicon) nitride, and combinations thereof. When atitanium-aluminum-silicon cathode target is used to sputter a coating inair, the deposited material can include titanium oxide, aluminum oxide,silicon oxide, (titanium-aluminum) oxide, (titanium-silicon) oxide,(aluminum-silicon) oxide, (titanium-aluminum-silicon) oxide, titaniumnitride, aluminum nitride, silicon nitride, (titanium-aluminum) nitride,(titanium-silicon) nitride, (aluminum-silicon) nitride,(titanium-aluminum-silicon) nitride, titanium oxynitride, aluminumoxynitride, silicon oxynitride, (titanium-aluminum) oxynitride,(titanium-silicon) oxynitride, (aluminum-silicon) oxynitride,(titanium-aluminum-silicon) oxynitride, and combinations thereof.

In the practice of the invention, silicon with combinations of oxides,nitrides, and oxynitrides can be used to provide the film of the instantinvention. As discussed in the following, titanium, aluminum oxide,nitride or combinations of oxide, nitride or oxynitride as dielectricand/or protective layers offer durable coatings with increasedflexibility in the choice of color and reflectance.

The dielectric and/or protective layer of the instant invention can be“homogeneous”, “graded” or “non-homogeneous”.

In the following examples, unless otherwise stated, the coatings weredeposited on a smaller scale, using planar magnetron cathodes having5×17 inch (12.7×43.2 centimeters) titanium-aluminum andtitanium-aluminum-silicon targets. Base pressure was in the low 10⁻⁵ to10⁻⁶ torr range. The coatings were made by first admitting thesputtering gas to a pressure ranging from 3 to 4 millitorr and thensetting the cathode at a constant power. In each example, clear floatglass substrates were passed under the target on a conveyor roll at aspeed of 120 inches (3.05 meters) per minute. The transmittance wasmonitored during the sputtering process at a wavelength of 550nanometers using a Dyn-Optics 580D optical monitor.

After the coating was deposited, the transmittance and reflectance fromboth the glass and coated surface were measured in the wavelength rangefrom 380 to 720 nanometers using a TCS spectrophotometer manufactured byBYK Gardner in Columbia, Md. This data was used with a commerciallyavailable software program to calculate the coating refractive index (n)and absorption coefficient (k), the integrated transmittance andreflectance. The thicknesses of the coatings were measured using aTencor P-1 Long Scan Profiler.

EXAMPLES

It was found that films containing a combination of Ti and Al producedseveral surprising features. Ranges of the metal mixture showedpreferential oxidation, relative to either of the pure metals oftitanium or aluminum films. Independently of this, an enhancement of thelow emissivity coating was realized when the metal mixture wasincorporated as a primer layer. A dramatic improvement in the long-termexposure to the environment of a thermally processed coating wasobserved. A range of the mixed metal primer showed no breakdown,compared to the pure metal primers after more than 1.5 years of exposurein the lab environment. In addition, the sheet resistance of the lowemissivity coating was lower for a range of the metal mixture thaneither of the pure metal primers. Both of these benefits clearlyindicate an improvement over the pure metal primers in the art.

Titanium-aluminum oxide and nitride coatings showed greatly enhancedchemical durability compared to a titanium dioxide coating, as indicatedby exposure to condensing humidity testing.

To produce thin film samples composed of a mixture of metals, a planarcathode target, i.e., a solid 5″×14″ (12.5 cm×35 cm) pure metal plate,was either a solid target composed of the specific metal mixture oralloy, or a split target divided into two, side-by-side 5″×7″ (2.5cm×17.5 cm) plates of the two metals. Specific Ti—Al alloys were usedfor the solid targets and were fabricated by Hot Isostatic Pressing(HIP) powders of the alloy, or Vacuum planar Induction skull Melting(VIM) and casting an ingot target from the metal powders, or plasmasprayed. Chemical analysis of the target alloy was used to determine theweight percent of the individual metals. Both the split and the specificalloy targets were bolted to a backing plate and then to the cathodeassembly.

The examples are arranged in two general areas: Examples 1-4 describethe Ti—Al sputtered coatings on glass; Examples 5-7 describe Ti—Allayers as part of a low emissivity coating stack.

Example 1 Mixed Metal or Alloys Sputtered from a Split Target of Pure Aland Ti

Samples G1 and G2

The split target produced coatings composed of a mixture of Al—Ti in asingle run. This mixture had a (non-linear) gradient composition acrossthe width of the glass sheet, and constant composition in the directionof travel. The gradient samples (G1) (G2) were produced on 12″×12″ (30cm×30 cm)—2.3 mm clear float glass in an Airco ILS chamber. The basepressure in the chamber before sputtering was 1.0×10-5 torr. The Al—Titarget was sputtered at a pressure of 3 microns in a 100% argon gasatmosphere. The power to the cathode target for sample G1 was 1 kilowattresulting in a voltage of 395 volts and a current of 2.52 amps. Thetarget was passed under the target 3 times at a speed of 120 inches perminute until the transmission was reduced to 20.9%. Sample G2 wasdeposited at a power of 5 kilowatts, resulting in a voltage of 509 voltsand a current of 9.72 amps. After 5 passes under the target, thetransmission was reduced to 0.1%. The transmission in the ILS coater isread in the center of the plate, therefore, the transmission reading isapproximately that for the center of the gradient layer. The values ofthe operating parameters for each sample are shown in Table A below.

After deposition using the split target, a 1.375 inch strip was cutperpendicular to the direction of travel (along the gradient) intoeight—1.375 inch (3.5 cm) squares for X-ray fluorescence (XRF) analysis.The average amount of titanium and aluminum in each individual sample interms of micrograms/cm² (μg/cm²) was calculated from these measurements.The weight percentage of Al and Ti was then calculated from the amountof μg/cm² for each sample. E.g., the center of XRF sample G1, located3.438 inches (8.7 cm) from the edge of the first sample, contains anaverage weight of 90.1% titanium. Rather than converting the centerposition of each XRF sample to inches or centimeters, a template wascreated marking the center position of each XRF sample along the widthof the sample plate. Therefore, G1 has the value 3 units on the templatewith a 90.1 wt % of titanium. The positions between the centers of eachsample are located at a fractional part of the distance betweenpositions on the template. The average composition of the mixed metalswas determined by averaging the weight percent of both samples (G1 andG2) for each position along the width of the plate. The micrograms/cm²and the weight for Al and Ti at each position for each sample are shownin Table B, along average of the samples at each position. A Sigmoid 5parameter fit was fit the data. The percent of Ti and Al for eachposition along the width of the d the calculated fit to the data isshown in FIG. 2.

The equation for the data fit is:Weight %=y ₀ +a/(1+exp((1+exp(−(x−x ₀)/b))^(c)

-   -   where a=0.9485        -   b=0.743        -   c=1.2513        -   x₀=4.3454

y₀=0.0226 TABLE A Power Number of Example # Voltage Current (kw) passesTransmittance G1 395 2.52 1.0 3 20.9 G2 509 9.72 5.0 5 0.1

TABLE B G1 G2 Avg. of G1, G2 sample microgm/cm² wt % microgm/cm² wt %average wt % position Al Ti Al Ti Al Ti Al Ti Al Ti 1 0.09 4.78 1.8 98.20.96 37.35 2.5 97.5 2.2 97.8 2 0.2 4.79 4.0 96.0 1.9 37.32 4.8 95.2 4.495.6 3 0.5 4.53 9.9 90.1 4.48 35.33 11.3 88.7 10.6 89.4 4 1.5 3.6 29.470.6 13.12 28.18 31.8 68.2 30.6 69.4 5 3.35 1.94 63.3 36.7 28.13 14.9465.3 34.7 64.3 35.7 6 4.32 0.82 84.0 16.0 36.7 5.74 86.5 13.5 85.3 14.77 4.56 0.35 92.9 7.1 38.91 2.33 94.4 5.6 93.6 6.4 8 4.54 0.18 96.2 3.838.86 1.15 97.1 2.9 96.7 3.3

Results of Oxidation by Heating Mixed Metal or Alloys Sputtered from aSplit Cathode

After the plate described above was heated to the bending point of sodalime glass, it was observed that a section of the plate of metal mixturehad oxidized, whereas the pure metal had not. For the Ti—Al mixture,this occurred at a position between 3.5 and 4.0 units on the template asindicated in Table B and FIG. 2. This corresponds to a weight percent oftitanium of 85 to 68 weight percent, respectively, as shown in Table Band FIG. 3. The range will be larger for thinner coatings, and narrowerfor thicker coatings.

The oxidation of the metal mixture makes it possible to apply thickercompositions of Ti—Al metal, e.g., as a metal overcoat layer forsubsequent oxidation during thermal processing. The metal mixture layercould also be oxidized by other methods that drive the temperature ofthe coating to the point of oxidation.

The metal mixture may segregate after heating, producing a layer withone metal richer than the other.

The metal mixture can also be sputtered in a gas mixture with a smallpercentage of a reactive gas (O₂ or N₂), below the switch point.

The target composed of the metal mixture, a compound or alloy of themetals can be sputtered in an inert, reactive or inert-reactive gas mix,such as argon, O₂, N₂ or combinations.

Example 2 Ti—Al Oxide and Nitride Films Sputtered from Ti-50Al andTi-30Al Alloy Targets

Alloys of Ti—Al oxide and nitride thin films coatings have shownsurprising results in Cleveland Condensation Chamber (CCC) testing(Q-T-C Cleveland Condensation Tester is manufactured by The Q-PanelCompany of Cleveland, Ohio). In comparison, aluminum oxide and nitridecoatings sputtered at room temperature are completely removed in an houror less when exposed in the CCC test chamber. Titanium dioxide (U.S.Pat. Nos. 4,716,086 and 4,786,563), nitride and oxynitrides, on theother hand, have good chemical durability and withstand days of exposurein the CCC test chamber before deteriorating. It was discovered thatalloys of Ti—Al oxide and nitride thin films far surpass the performanceof titanium dioxide in the CCC test chamber.

The coatings were deposited in an Airco ILS 1600 coater on 12″×12″ (30cm×30 cm) square by 2.3 mm thick clear float glass substrates at ambienttemperature. The substrate was conveyed at a line speed of the 120inches per minute. The base pressure was in the low 10⁻⁵ torr range andthe operating pressure was 4 microns (m torr). The substrate was atambient temperature during deposition. Planar targets of Ti-30Al andTi-50Al, where the amount of aluminum is expressed in atomic percent,were manufactured (except where noted) by Hot Isostatic Pressing (HIP)powders of the alloy. The alloy oxide films were deposited in anatmosphere of 50% argon and 50% oxygen.

Sample E1

A Ti-50Al oxide sample was run at a power setting of 3.0 kilowatts, witha voltage of 432 volts and a current of 6.98 amps. After 10 passes, thetransmission was 91.2% and the thickness was 114 Angstroms.

Sample E2

A second Ti-50Al oxide sample was run at a power setting of 4.0kilowatts with a voltage of 494 volts and current 8.14 amps. Thetransmission was 87.5% after 10 passes and the thickness was 274Angstroms.

Sample E3

A Ti-30Al oxide sample was run a power setting of 3.0 kilowatts with avoltage 490 volts, and the current of 6.14 amps. The transmission was91.3% after 10 passes and the thickness was 89 Angstroms.

Sample E4

A Ti-50Al nitride sample was run in an atmosphere of 100% nitrogen at apower setting of 3.0 kilowatts with a voltage of 640 volts and a currentof 4.72 amps. The transmission was 30.5% after 15 passes and thethickness was 713 Angstroms.

Comparative Sample CE1

The titanium dioxide sample, shown for comparison, was run at a powersetting of 4.0 kilowatts with a voltage 451 volts, and a current of 8.86amps. The transmission was 88.2% after 10 passes and the thickness was92 Angstroms.

Table C summarizes the target material, coater setting and resultingcoating.

Cleveland Condensation Chamber (CCC) Exposure Test Results for SamplesE1 to E4 and CE1

The Ti-30Al and 50Al oxide thin films showed no deterioration afterweeks of exposure in the CCC test chamber. This was an unexpected resultfor these alloy oxides, considering the poor behavior of aluminum oxidein the CCC test; it would be expected that the addition of aluminumoxide would decrease the corrosion resistance of the alloy. Rather, thepresence of aluminum enhances the corrosion resistance over that oftitanium oxide. Longer term testing of the alloy oxides shows that theTi-50Al oxide is even more corrosion resistant than the Ti-30Al oxide.This is an even more surprising result given the higher concentration ofaluminum in the coating.

FIG. 4 (which is the same as FIG. 5 but with an expanded scale) showsthe change in integrated reflectance (Y(R1)) of the coated surface as afunction of exposure time in hours in the CCC. The TiO₂ film is shownfor comparison. After at least 350 hours of exposure there is nosignificant change in the coating reflectance. The TiO2 shows a smallchange after 28 hours followed by a rapid decrease in reflectanceindicating rapid coating degradation. After 200 hours, the coating isaround 8%, which is the reflectance of the uncoated glass substrate.This indicates that the coating has been completely removed. FIGS. 4 and5 show long-term behavior of the Ti—Al oxide coatings in the CCC testchamber. The Ti-50Al oxide coating shows a slower decrease inreflectance than the Ti-30Al oxide coating indicating slower degradationof the coating. As noted earlier, this is surprising considering thehigher amount of aluminum in the coating. FIG. 6 shows the 274 AngstromTi-50Al oxide coating. The behavior is similar to the thinner film witha slow, rather than rapid decrease in reflectance, as shown by TiO2film.

A Ti-50Al nitride thin film has shown similar or better results in CCCtest chamber exposure. Again, this is surprising considering the highsusceptibility of aluminum nitride to water corrosion. FIG. 7 shows theIntegrated Reflectance (Y(R1)) from the coated surface as a function ofthe exposure time in hours in the CCC chamber. There is less than a 1%change in reflectance after almost 2000 hours of exposure. Visualinspection of the Ti-50Al nitride film showed no noticeable degradationas compared to the unexposed section of the coating. TABLE C XRF SampleTarget ILS Coater Settings Thickness (ug/cm²) Wt % No. Alloy KW PassVolts Amps ILS % T Gas (Å) Al Ti Al Ti E1 Ti—50Al 3.0 10 432 6.98 91.250%O2-Ar 114 .58 1.19 33.9 66.1 E2 Ti—50Al 4.0 20 494 8.14 87.5 50%O2-Ar274 E3 Ti—30Al 3.0 10 490 6.14 91.3 50%O2-Ar 89 .26 1.19 18.7 81.3 E4Ti—50Al 3.0 15 640 4.72 30.5 100%N2 713 CE1 Ti 4.0 10 451 8.86 88.250%O2-Ar 92 .00 1.89 0.0 100

Example 3 Ti—Al Oxide Films Sputtered from Ti-90Al and Ti-10Al AlloyTargets

Ti—Al metal films were deposited in an Airco ILS 1600 coater on 12″×12″(30 cm×30 cm) square by 2.3 mm thick clear float glass substrates atambient temperature. The substrate was conveyed at a line speed of 120inches (300 cm) per minute. The base pressure was in the low 10⁻⁶ torrrange and the operating pressure was 4 microns. Planar targets ofTi-10Al and Ti-90Al, where the amount of aluminum is expressed in atomicpercent, were used to deposit the coatings. The Ti-10Al target wasmanufactured by Hot Isostatic Pressing (HIP) the alloy powder. Analysisof the target material indicated 5.85 weight percent aluminum with thebalance titanium. The Ti-90Al target was manufactured by vacuuminduction skull melting and casting an ingot target from the metalpowders. Analysis of the target material indicated 16.3 weight percenttitanium with the balance aluminum. The alloy films were deposited in anatmosphere of 80% argon and 20% oxygen gas mixture.

Sample E6

A Ti-90Al metal film sample was run at a power setting of 4 kilowatts,with a voltage of 419 volts and a current of 9.5 amps. The transmissionwas 90.1% after 10 passes under the target and the thickness wasmeasured at 166 Angstroms.

Sample E7

A Ti-90Al metal film sample was run at a power setting of 4.0 kilowatts,with a voltage of 404 volts and a current of 9.5 amps. The transmissionwas 88.7% after 20 passes under the target and the thickness wasmeasured at 365 Angstroms.

Sample E8

A Ti-90Al metal film sample was run at a power setting of 4 kilowatts,with a voltage of 400 volts and a current of 9.95 amps. The transmissionwas 87.1% after 30 passes under the target and the thickness wasmeasured at 583 Angstroms.

Sample E9

A Ti-10Al metal film sample was run at a power setting of 4 kilowatts,with a voltage of 534 volts and a current of 7.45 amps. The transmissionwas 88.0% after 10 passes under the target and the thickness wasmeasured at 135 Angstroms.

Sample E10

A Ti-10Al metal film sample was run at a power setting of 4.0 kilowatts,with a voltage of 536 volts and a current of 7.4 amps. The transmissionwas 81.5% after 20 passes under the target and the thickness wasmeasured at 278 Angstroms.

Sample E11

A Ti-10Al metal film sample was run at a power setting of 4.0 kilowatts,with a voltage of 532 volts and a current of 7.45 amps. The transmissionwas 75.2% after 30 passes under the target and the thickness wasmeasured at 407 Angstroms.

Table D summarizes the target material, coater settings, and resultingcoating.

Table E illustrates the sputtering rate for various combinations oftarget material (based on the atomic percentage of each component) interms of Angstroms per kilowatt-pass.

FIG. 8 plots the sputtering rate for the different targets shown inTable E. TABLE D XRF Sample Target ILS Coater Settings Thickness(ug/cm{circumflex over ( )}2) Wt % No. Alloy KW Pass Volts Amps ILS % TGas (Å) Al Ti Al Ti E6 Ti—90Al 4 10 419 9.5 90.1 80%O₂/Ar 166 1.84 0.4480.7% 19.3% E7 Ti—90Al 4 20 404 9.5 88.7 80%O₂/Ar 365 3.73 0.87 81.1%18.9% E8 Ti—90Al 4 30 400 9.95 87.1 80%O₂/Ar 583 5.75 1.28 81.8% 18.2%E9 Ti—10Al 4 10 534 7.45 88 80%O₂/Ar 135 0.15 2.34 6.0% 94.0% E10Ti—10Al 4 20 536 7.4 81.5 80%O₂/Ar 278 0.29 4.96 5.5% 94.5% E11 Ti—10Al4 30 532 7.45 75.2 80%O₂/Ar 407 0.41 7.28 5.3% 94.7%

TABLE E Sputtering Rate (Angstroms per kilowatt-pass) for Ti—Al OxideCoatings Ti—Al target in 80%O2/Ar Gas mixture Å/kwp Sample Target Pressno. kw*pass Voltage Current ILS Thickness Avg. (Least No. material μpass kw (kwp) (volts) (amps) % T (Å) wt % Al sq fit) R² CE2 Al 4 120 1120 283 3.44 89.4 422 0.00 3.54 0.999 CE3 Al 4 80 1 80 289 3.36 89.5 284CE4 Al 4 40 1 40 285 3.48 89.9 146 CE5 Ti 4 30 4 120 493 8.06 74.6 3581.00 3.01 0.990 CE6 Ti 4 20 4 80 490 7.94 82.5 239 CE7 Ti 4 10 4 40 5067.9 88.2 136 E11 Ti—10Al 4 30 4 120 532 7.45 75.2 407 0.06 3.38 0.985E10 Ti—10Al 4 20 4 80 536 7.4 81.5 278 E9 Ti—10Al 4 10 4 40 534 7.45 88135 E12 Ti—10Al 4 30 4 120 514 7.6 74 396 E13 Ti—10Al 4 20 4 80 539 7.3681.8 274 E14 Ti—10Al 4 10 4 40 548 7.27 88 121 E15 Ti—10Al 4 5 4 20 5457.31 89.5 101 E16 Ti—30Al 4 30 4 120 509 7.8 81.2 358 0.17 3.04 0.967E17 Ti—30Al 4 20 4 80 544 7.3 85.9 210 E18 Ti—30Al 4 10 4 40 553 7.288.9 123 E19 Ti—30Al 4 30 4 120 601 6.66 80.7 379 E20 Ti—30Al 4 20 4 80602 6.65 85.2 256 E21 Ti—30Al 4 10 4 40 603 6.63 88.9 141 E22 Ti—50Al 530 4 120 423 9.42 84.2 384 0.33 3.34 0.948 E23 Ti—50Al 5 20 4 80 4608.65 87.5 258 E24 Ti—50Al 5 10 4 40 459 8.67 89.5 91 E25 Ti—50Al 4 30 4120 460 8.73 83.6 409 E26 Ti—50Al 4 20 4 80 479 8.35 86.4 314 E27Ti—50Al 4 10 4 40 477 8.36 89.1 128 E8 Ti—90Al 4 30 4 120 400 9.95 87.1583 0.80 4.96 0.967 E7 Ti—90Al 4 20 4 80 404 9.5 88.7 365 E6 Ti—90Al 410 4 40 419 9.5 90.1 166 E28 Ti—90Al 4 30 4 120 392 9.65 86.8 600 E29Ti—90Al 4 20 4 80 395 9.71 86 452 E30 Ti—90Al 4 10 4 40 408 9.56 88.4210

Example 4 Ti—Al Metal Films Sputtered from Ti—Al Metal Targets

Ti—Al metal films were deposited in an Airco ILS 1600 coater on 12″×12″(30 cm×30 cm) square by 2.3 mm thick clear float glass substrates atambient temperature. The substrate was conveyed at a line speed of 120inches per minute. The base pressure was in the low 10⁻⁵ torr range andthe operating pressure was 4 microns. Planar targets of Ti-30Al andTi-50Al, where the amount of aluminum is expressed in atomic percent,were manufactured by Hot Isostatic Pressing (HIP) powers of the alloypowder. A planar target of Ti-90Al, where the amount of aluminum isexpressed in atomic percent, was made by Vacuum Induction skull Melting(VIM) and casting an ingot target from the metal powders. The alloyfilms were deposited in an atmosphere of 100% argon gas.

Sample D1

A Ti-30Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 529 volts and a current of 5.72 amps. The transmissionwas 21.3% after 1 pass under the target and the thickness was measuredat 161 Angstroms.

Sample D2

A Ti-30Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 529 volts and a current of 5.7 amps. The transmissionwas 8.5% after 2 passes under the target and the thickness was measuredat 270 Angstroms.

Sample D3

A Ti-30Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 529 volts and a current of 5.72 amps. The transmissionwas 0% after 5 passes under the target and the thickness was measured at704 Angstroms.

Sample D4

A Ti-30Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 528 volts and a current of 5.70 amps. The transmissionwas 0% after 10 passes under the target and the thickness was measuredat 1306 Angstroms.

Sample D5

A Ti-50Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 610 volts and a current of 4.94 amps. The transmissionwas 19.1% after 1 pass under the target and the thickness was measuredat 169 Angstroms.

Sample D6

A Ti-50Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 609 volts and a current of 4.96 amps. The transmissionwas 7.4% after 2 passes under the target and the thickness was measuredat 312 Angstroms.

Sample D7

A Ti-50Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 605 volts and a current of 5.0 amps. The transmissionwas 0% after 5 passes under the target and the thickness was measured at756 Angstroms.

Sample D8

A Ti-50Al metal film sample was run at a power setting of 3.0 kilowatts,with a voltage of 603 volts and a current of 5.0 amps. The transmissionwas 0% after 10 passes under the target and the thickness was measuredat 1500 Angstroms.

Sample D9

A Ti-90Al metal film was deposited at a power setting of 3.0 kilowatts,with a voltage of 827 volts and a current of 3.18 amps. The transmissionwas 8.8% after 1 pass under the target and the thickness was measured at162 Angstroms.

Sample D10

A Ti-90Al metal film was deposited at a power setting of 3.0 kilowatts,with a voltage of 827 volts and a current of 3.13 amps. The transmissionwas 2.1% after 1 pass under the target and the thickness was measured at311 Angstroms.

Sample D11

A Ti-90Al metal film was deposited at a power setting of 3.0 kilowatts,with a voltage of 827 volts and a current of 3.15 amps. The transmissionwas 0.0% after 1 pass under the target and the thickness was measured at756 Angstroms.

Sample D12

A Ti-90Al metal film was deposited at a power setting of 3.0 kilowatts,with a voltage of 827 volts and a current of 1.13 amps. The transmissionwas 0.0% after 1 pass under the target and the thickness was measured at1505 Angstroms.

Table F summarizes the target material, coater settings, and resultingcoating. TABLE F Sample Target ILS Coater Settings Thickness Microgm/cm²Wt % No. Alloy KW Pass Voltage Current ILS % T Gas (Å) Al Ti Al Ti D1Ti30Al 3.0 1 529 5.72 21.3 Ar 161 0.88 4.13 17.3 82.7 D2 Ti30Al 3.0 2529 5.70 8.5 Ar 270 1.76 8.48 17.1 82.9 D3 Ti30Al 3.0 5 529 5.72 0.0 Ar704 4.31 21.31 16.8 83.2 D4 Ti30Al 3.0 10 528 5.70 0.0 Ar 1306 8.2442.29 16.3 83.7 D5 Ti50Al 3.0 1 610 4.94 19.1 Ar 169 1.81 3.56 33.6 66.4D6 Ti50Al 3.0 2 609 4.96 7.4 Ar 312 3.49 6.83 33.8 66.2 D7 Ti50Al 3.0 5605 5.00 0.0 Ar 756 8.66 17.80 32.7 67.3 D8 Ti50Al 3.0 10 603 5.00 0.0Ar 1500 16.58 35.17 32.0 68.0 D9 Ti—90Al 3.0 1 827 3.18 8.8 Ar 162 3.260.87 78.9 21.1 D10 Ti—90Al 3.0 2 827 3.13 2.1 Ar 311 6.44 1.69 79.2 20.8D11 Ti—90Al 3.0 5 827 3.15 0.0 Ar 756 15.99 4.13 79.5 20.5 D12 Ti—90Al3.0 10 827 3.13 0.0 Ar 1505 31.02 7.85 79.8 20.2

Example 5 Ti—Al Primer Layers Sputtered from Al and Ti Split Target

Sample G3

A 12×12 inch (30 cm×30 cm) soda-lime glass substrate was placed in anAirco ILS coater with a base pressure of 1.1×10-5 torr. The layersequence for the low emissivity coating was:Glass/zinc stannate/Al—Ti primer/silver/Al—Ti primer/zinc stannate.

The first layer of an alloy of zinc and tin of 48% tin and 52% zinc byweight was deposited at 4 microns pressure in an atmosphere of 50%/50%mix by flow of argon and oxygen. The power to the cathode target was setat 1.7 kilowatts resulting in a voltage of 395 volts and a current of4.30 amps. The glass was passed under the cathode 4 times until thetransmission reached 81.9%. The second layer was deposited using thegradient cathode described earlier. The pressure in the chamber was 3microns in a 100% argon gas atmosphere. The power to the cathode was setat 0.4 kilowatts, resulting in a voltage of 348 volts and a current of1.14 amps. The glass was passed under the cathode 1 time, resulting in atransmission of 66.7%. The third layer was deposited using a silvercathode. The pressure in the chamber was 3 microns in a 100% argon gasatmosphere. The power to the cathode was set at 0.6 kilowatts, resultingin a voltage of 394 volts and a current of 1.52 amps. The glass waspassed under the cathode 1 time, which resulted in a transmission of50.9%. The fourth layer was deposited under the same conditions as thesecond layer. The transmission after this layer was 41.0%. The fifth andfinal layer was deposited under the same conditions as the first layer.The final transmission was 72.0%. The conveyor speed was 120 inches perminute. The coating was then heated to above the bending point of glass.

The sample was kept in the open environment of the lab for more than 1.5years and then reevaluated. It was found that a coating had broken downin a pattern that followed the Ti/Al gradient as shown in Table B andFIG. 3. The aluminum end of the sample showed large areas of coatingthat had completely broken down; the titanium end showed spotty areas ofcoating breakdown, typical of coating that has been in a unprotectedenvironment for an extended period of time. Surprisingly, there was anarea of the coating that clearly showed no breakdown in the region wherealuminum and titanium were mixed. Since the sheet resistance of thecoating tends to increase as the coating degrades, measurements weremade along the gradient of the coating. Although the resistance valueswere not made initially, the lower values of the sheet resistancecorresponded to the section of the coating that showed no breakdown overthe time period.

All areas measured were selected along the width of the sample fromregions where the coating had not yet broken down. An Allessi 4-pointprobe was used with a Kiethley System digital multimeter to make thesheet resistance measurements. Where possible, several measurements weremade at each location along the gradient and the standard deviation wascalculated. In some locations where there was a large amount ofbreakdown only one measurement was possible. The calibrated template wasused to determine the percentage of titanium and aluminum at each pointalong the width of the sample where the sheet resistance measurementswere made. The sheet resistance for the low emissivity coating for eachposition along the template is shown in FIG. 9. The error bars denote+/− one standard deviation.

FIGS. 3 and 10 show the sheet resistance as a function of the weightpercentage of titanium and aluminum, respectively, in the primer layersof the low emissivity coating. The graph shows that for values of wt %titanium greater than 10% and less than 80% the resistance of thecoating is lower than the pure metal or low percentage mixture. There isa steep rise in resistance for coatings less than 10% aluminumindicating that the aluminum primer, even after heating, is unstableafter exposure in an unprotected environment. For values of titaniumgreater than 80% there is a leveling off in the value of the resistance,indicating that typical behavior of coatings common in the art today.The coating in the range of 10 to 80 weight percent titanium, with thebalance of aluminum, not only has lower sheet resistance but also hasincreased stability when left unprotected. The corresponding atomicweights are shown in FIGS. 11 and 12.

Example 6 Ti—Al Primer Layers Sputtered from Ti-50Al and Ti-30Al AlloyTargets

Primer layers using Ti—Al alloy targets were used to make samples of lowemissivity coatings with the coating the layer sequence:Glass/zinc stannate/silver/Al—Ti/zinc stannate.The coating configuration differs from the gradient target configuration(sample G3) with the omission of the alloy layer below the silver layer.The following examples illustrate the functionality of the alloy layercompared to a titanium layer, which is used in the art. (U.S. Pat. Nos.4,898,789 and 4,898,790)

The planar targets used for the primer layer above the silver wereTi-30Al and Ti-50Al, where the amount of aluminum is expressed in atomicpercent, were manufactured by Hot Isostatic Pressing (HIP) powders ofthe alloy. Analysis of the Ti-30Al target material indicated 19.19weight percent aluminum with the balance titanium. Analysis of theTi-50% target material indicated 36.48 weight percent aluminum with thebalance titanium. A pure titanium target was used to produce primersamples for comparison with the alloy primers.

Sample B1

A 12 inch×12 inch (30 cm×30 xm) by 2.3 mm thick clear float glasssubstrate was placed in an Airco ILS coater with a base pressure in thelow 10⁻⁵ Torr. The first layer of an alloy of zinc and tin of 48% tinand 52% zinc by weight was deposited at 4.0 microns pressure in anatmosphere of 80% argon gas and 20% oxygen gas mixture as set on theflow controller. The power to the cathode target was set at 2.2kilowatts resulting in a voltage of 360 volts and a current of 6.12amps. The glass was passed under the cathode 5 times at a conveyor speedof 120 inches per minute (3.05 meters per minute) until the transmissionreached 81.2%. The thickness of the first layer was 312 Angstroms. Thesecond layer was deposited using a silver cathode. The pressure in thechamber was 4.0 microns in a 100% argon gas atmosphere. The power to thecathode was set at 0.6 kilowatts, resulting in a voltage of 458 voltsand a current of 1.32 amps. The glass was passed under the cathode 1time, which resulted in a transmission of 64.2%. The thickness of thesecond layer was 111 Angstroms. The third layer was deposited using theTi-30Al target at a power setting of 0.3 kilowatts, with a voltage of354 volts and a current of 0.86 amps. The thickness of the Ti—Al primerlayer was calculated to be 13 Angstroms after 1 pass the transmissionwas 55.60%. The fourth and final layer was deposited under the sameconditions as the first layer, resulting in a final transmission of thecoating of 87.0%. The sheet resistance after coating was 5.96 ohms persquare. The coated glass substrate was then heated for 5 minutes at 704°C. (1300° F.) resulting in a substrate temperature of 649° C. (1200°F.). The electrical sheet resistance was infinite and the transmittancewas 77.4% after heating.

Sample B2

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti-30Al target at a power setting of 0.6kilowatts, with a voltage of 390 volts and a current of 1.56 amps. Thetransmission was 47.1% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 79.6%. The sheet resistance after coating was 7.85 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 82.9% and the electrical sheet resistance was 9.1 ohmsper square after heating.

Sample B3

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti-30Al target at a power setting of 0.9kilowatts, with a voltage of 410 volts and a current of 2.20 amps. Thetransmission was 40.3% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 68.5%. The sheet resistance after coating was 7.15 ohms per square.The coating was then heated by the method described above for Sample B1.The transmittance was 83.5% and the electrical sheet resistance was 6.6ohms per square after heating.

Sample B4

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti-30Al target at a power setting of 1.2kilowatts, with a voltage of 423 volts and a current of 2.84 amps. Thetransmission was 35.2% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 60.7%. The sheet resistance after coating was 7.66 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 74.8% and the electrical sheet resistance was 8.40ohms per square after heating.

Sample B5

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of example B1. The third layer was deposited by passingthe glass one time under the Ti-50Al target at a power setting of 0.3kilowatts, with a voltage of 380 volts and a current of 0.82 amps. Thetransmission was 52.4% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 86.2%. The sheet resistance after coating was 6.97 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 84.7% and the electrical sheet resistance was 13.6ohms per square after heating.

Sample B6

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti-50Al target at a power setting of 0.6kilowatts, with a voltage of 426 volts and a current of 1.42 amps. Thetransmission was 44.1% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 74.3%. The sheet resistance after coating was 8.46 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 85.1% and the electrical sheet resistance was 6.9 ohmsper square after heating.

Sample B7

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti-50Al target at a power setting of 0.9kilowatts, with a voltage of 458 volts and a current of 1.98 amps. Thetransmission was 37.6 after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 63.7%. The sheet resistance after coating was 8.20 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 80.6% and the electrical sheet resistance was 8.9 ohmsper square after heating.

Sample B8

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti-50Al target at a power setting of 1.2kilowatts, with a voltage of 482 volts and a current of 2.52 amps. Thetransmission was 32.6% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 55.5%. The sheet resistance after coating was 8.08 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 72.9% and the electrical sheet resistance was 13.1ohms per square after heating.

Sample CB1

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti target at a power setting of 0.3kilowatts, with a voltage of 317 volts and a current of 0.96 amps. Thetransmission was 54.6 after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 87.3%. The sheet resistance after coating was 6.36 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 74.6% and the electrical sheet resistance was infiniteafter heating.

Sample CB2

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti target at a power setting of 0.6kilowatts, with a voltage of 340 volts and a current of 1.78 amps. Thetransmission was 46.6 after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 80.1%. The sheet resistance after coating was 7.42 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 82.3% and the electrical sheet resistance was 7.90ohms per square after heating.

Sample CB3

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti target at a power setting of 0.9kilowatts, with a voltage of 354 volts and a current of 2.56 amps. Thetransmission was 39.5% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 68.8%. The sheet resistance after coating was 7.85 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 79.7% and the electrical sheet resistance was 6.50ohms per square after heating.

Sample CB4

The first and fourth layer were deposited from the alloy target of zincand tin, and the second layer of was deposited from the silver target bythe same method of Sample B1. The third layer was deposited by passingthe glass one time under the Ti target at a power setting of 1.2kilowatts, with a voltage of 364 volts and a current of 3.32 amps. Thetransmission was 33.9% after deposition of the third layer. The finaltransmittance of the coating after the deposition of the fourth layerwas 59.6%. The sheet resistance after coating was 7.78 ohms per square.The coating was then heated by the method described for Sample B1. Thetransmittance was 74.0% and the electrical sheet resistance was 8.2 ohmsper square after heating.

Table G summarized the target material, coater settings, and resultingcoatings. TABLE G Ti—Al Primer Layers ILS Coater Settings SheetResistance % Transmittance Sample Target Power Voltage Current Thickness(ohms/square) ILS TCS No. material (kilowatts) Pass (volts) (amps)(Angstroms) before heat after heat before heat after heat B1 Ti—30Al 0.31 354 1.32 13 5.96 ∞ 87.0 77.04 B2 Ti—30Al 0.6 1 390 1.56 27 7.85 9.179.6 82.84 B3 Ti—30Al 0.9 1 410 2.20 40 7.51 6.6 68.5 83.49 B4 Ti—30Al1.2 1 423 2.84 53 7.66 8.4 60.7 74.83 B5 Ti—50Al 0.3 1 380 0.82 15 6.9713.6 86.2 84.73 B6 Ti—50Al 0.6 1 426 1.42 30 8.46 6.9 74.3 85.16 B7Ti—50Al 0.9 1 458 1.98 45 8.2 8.9 63.7 80.65 B8 Ti—50Al 1.2 1 482 2.5260 8.08 13.1 55.5 72.93 CB1 Ti 0.3 1 317 0.96 13 6.35 ∞ 87.3 74.55 CB2Ti 0.6 1 340 1.78 25 7.42 7.9 80.1 82.28 CB3 Ti 0.9 1 354 2.56 38 7.856.5 68.8 79.72 CB4 Ti 1.2 1 364 3.32 51 7.78 8.2 59.6 73.96Results—Ti—Al Primer Layers

FIG. 13 shows the behavior of the sheet resistance with primer thicknessof the Ti-30Al and the Ti-50Al primers before heating. The Ti primer isshown as a comparison to the alloy primers. The primers behave similarlywith the Ti-50Al primer having a slightly higher resistance than the Tiand Ti-30Al primers.

FIG. 14 shows the behavior of the sheet resistance with primer thicknessof the Ti-30Al and the Ti-50Al primers after heating. The Ti primer isshown as a comparison to the alloy primers. The Ti-50 primer is stillelectrically conductive with a primer layer less than 20 Angstroms,indicating a continuous silver layer after heating. The Ti and Ti-30Alprimers are not conductive after heating with a primer layer less than25 Angstroms, and consequently the silver layer is not continuous. Theprimer layers attain a minimum sheet resistance of 6.5 ohms per square,but the Ti-50Al primer attains the minimum resistance at a lowerthickness. All the primer layers sharply increase in electricalresistance beyond the minimum resistance.

FIG. 15 shows the behavior of the transmittance of the coating in theILS coater with primer thickness of the Ti-30Al and the Ti-50Al primersbefore heating. The Ti primer is shown as a comparison to the alloyprimers. The transmittance of the coating decreases with increasingthickness for the primers. All primers show about the same behavior.This is due to the increasing absorption of the primer layers withincreasing thickness.

FIG. 16 shows the behavior of the transmittance of the coating, asmeasured on the TCS spectrophotometer, with primer thickness of theTi-30Al and the Ti-50Al primers after heating. The Ti primer is shown asa comparison to the alloy primers. Surprisingly, the Ti-50Al primerlayer has higher transmittance than the Ti and Ti-30Al primer layers.There is a range of thin primer layers where the chart indicates aconstant high transmittance from 15 to 30 Angstroms. This is highlydesirable, particularly when minimum light transmittance requirementsimpose limitations on coating performance, e.g., the 70% and 75% lighttransmittance requirements (Illuminant A) for windshields in the U.S.and Europe, respectively.

Example 7 Ti—Al and Ti—Al Oxide Overcoat Layers Sputtered over LowEmissivity Coatings

Low emissivity coatings with the coating the layer sequence:Glass/zinc stannate/silver/titanium/zinc stannate/Ti—Al oxide or Ti—Alwere deposited in an Airco ILS 1600 coater on 12″×12″ (30.5 cm×30.5 cm)square, by 2.3 mm thick clear float glass substrates at ambienttemperature. The substrate was conveyed at a line speed of the 120inches per minute (3.05 m per minute). The base pressure was in the low10⁻⁶ Torr range and the operating pressure was microns (m Torr). Thesubstrate was at ambient temperature during deposition. Planar targetsof Ti—Al alloy, where the amount of aluminum is expressed in atomicpercent, were used to deposit metal oxide or metal films over the lowemissivity coatings, as indicated in the above layer sequence. Ti-30 andTi-50Al alloy targets were fabricated by Hot Isostatic Pressing (HIP)powders of the alloy. The Ti-90Al alloy target was made by VacuumInduction skull Melting (VIM) and casting an ingot target from the metalpowders. Chemical analysis of the alloy was used to determine the weightpercent of the individual metals. The alloy oxide films were depositedin an atmosphere of a mixture of 20% argon and 80% oxygen gas. The alloyfilms were deposited in 100% argon gas. The coatings with Ti—Alovercoats on the low emissivity were compared with titanium oxideovercoats and no overcoats on the low emissivity coating. The targetcompositions are shown in Table H below.

4 inch×4 inch (10.2 cm×10.2 cm)×2.3 mm thick samples of coated glasswere heated in a Thermolyne Type 30400 Furnace set at 1300° F. (703°C.). The samples were placed on a 3.5 inch×3.5 inch (8.9 cm×8.9 cm)bending iron and placed in the furnace for 240 seconds. The coated glassattains a temperature of 1170° F. (632° C.) in that time as determinedby thermocouple measurements of similar low emissivity coatings. Sheetresistance and transmittance of the coating were recorded both beforeand after the heating in the furnace. The transmittance was read in theILS coater before heating and on the TCS meter after heating. TABLE HTarget Composition Ti—Al Target Composition Analysis Method of TargetTi— at % Al wt % Al (balance Ti) Fabrication Ti—10Al 5.85 HIP Ti—30Al19.2 HIP Ti—50Al 36.48 HIP Ti—90Al 16.3 I VIM Ti—75Al 63.3 Plasma SpraySample F13

The first layer of an alloy of zinc and tin of 48% tin and 52% zinc byweight was deposited in an atmosphere of 20% argon gas and 80% oxygengas mixture as set on the flow controller. The power to the cathodetarget was set at 2.14 kilowatts resulting in a voltage of 385 volts anda current of 5.56 amps. The glass was passed under the cathode 6 timesat a conveyor speed of 120 inches per minute (3.05 meters per minute)until the transmission reached 80.3%. The thickness of the first layerwas 426 Angstroms. The second layer was deposited using a silver cathodein a 100% argon gas atmosphere. The power to the cathode was set at 0.40kilowatts, resulting in a voltage of 437 volts and a current of 0.91amps. The glass was passed under the cathode 1 time, which resulted in atransmission of 65.7%. The thickness of the second layer was 95Angstroms. The third layer was deposited using a titanium target at apower setting of 0.42 kilowatts, with a voltage of 322 volts and acurrent of 1.30 amps. The thickness of the titanium primer layer wascalculated to be 20 Angstroms after 1 pass the transmission was 51.2%.The fourth layer was deposited under the same conditions as the firstlayer, resulting in a transmission of 83.5%. The overcoat layer wasdeposited by passing the glass 3 times under the Ti-90Al target, in anatmosphere of 20% argon gas and 80% oxygen gas mixture, at a powersetting of 3.10 kilowatts, with a voltage of 373 volts and a current of8.28 amps. The final transmittance of the coating after the depositionof the overcoat layer was 82.1% and after heating was 85.9%. Theovercoat thickness is 50 Angstroms. The sheet resistance after coatingwas 9.07 ohms per square after deposition and 7.88 ohms per square afterheating.

Samples F1-F12, F14-F22, FC1-5

The first and fourth layer were deposited from the alloy target of zincand tin, the second layer was deposited from the silver target, and thethird layer was deposited from the titanium target in a similar mannerto Sample F13. The silver and ZnSn oxide thicknesses are shown in theTable I: Ti—Al Overcoat Layers on Low Emissivity Coating. The oxideovercoat layer (F1-F14) was deposited by passing the glass with the lowemissivity coating under the Ti—Al target or Ti target (FC1), set at aconstant power on the power supply, in an atmosphere of 20% argon and80% oxygen. The metal overcoat layer (F15-F22) was deposited bysputtering in a gas of 100% argon. The voltage and currents for eachpower setting for the overcoats are shown in Table I. The overcoatthickness, the final transmittance of the coating after the depositionand after heating, and the sheet resistance after deposition and afterheating, along with the percent change in sheet resistance are shown inTable I. Samples with no overcoat layer (FC3-5) are indicated by 0thickness in the Overcoat Layer section of the Table I. TABLE I Ti—AlOvercoat Layers over Low Emissivity Coating Low Emissivity Coating(includes overcoat layer) Percent Overcoat Layer Transmittance SheetResistance Thickness (Å) Passes TCS (ohms/sq) ZnSn Target Process underPower Supply Readings Thickness After Before After % Oxide Ag Sample #Material gas target Kw Voltage Current (Å) ILS Heat Heat Heat changelayer layer FC1 Ti Ar—80O₂ 4 2.4 477 5.00 32 83.0 84.27 8.27 7.94 −3.99417 101 F1 Ti—10Al Ar—80O₂ 4 2.26 491 4.60 26 82.7 85.03 6.87 6.22 −9.46435 110 F2 Ti—10Al Ar—80O₂ 4 3.77 518 7.30 47 82.3 82.09 8.29 8.31 0.24439 101 F3 Ti—30Al Ar—80O₂ 4 2.5 528 4.74 26 83.3 85.59 8.24 6.69 −18.81431 103 F4 Ti—30Al Ar—80O₂ 4 3.8 565 6.72 46 82.8 84.85 8.27 6.52 −21.16434 104 F5 Ti—30Al Ar—80O₂ 4 3.8 561 6.78 57 82.3 83.5 8.77 7.36 −16.08449 97 F6 Ti—30Al Ar—80O₂ 4 4 575 6.69 71 83.0 84.92 7.97 7.24 −9.16 411101 F7 Ti—30Al Ar—80O₂ 6 4 560 7.15 75 82.0 83.95 8.75 8.87 1.37 436 101F8 Ti—50Al Ar—80O₂ 4 2.2 402 5.47 34 82.9 86.44 7.66 6.17 −19.45 418 106F9 Ti50Al Ar—80O₂ 4 2.9 414 7.00 48 82.0 86.33 7.7 6.7 −12.99 353 114F10 Ti50Al Ar—80O₂ 5 3.5 433 8.08 70 81.9 86.61 7.82 7.36 −5.88 304 104F11 Ti—50Al Ar—80O₂ 4 3.6 436 8.26 73 82.0 83.6 8.83 7.78 −11.89 434 95F12 Ti90Al Ar—80O₂ 2 2.6 381 6.81 21 82.9 87.3 7.98 6.26 −21.55 386 103F13 Ti—90Al Ar—80O₂ 3 3.1 373 8.28 50 82.1 85.9 9.07 7.88 −13.12 427 95F14 Ti90Al Ar—80O₂ 4 3.5 384 9.06 70 81.5 86.51 7.25 5.78 −20.28 403 113FC2 Ti Ar 1 0.65 336 1.93 31 47.1 82.44 7.91 7.05 −10.87 424 101 F15Ti—10Al Ar 1 0.55 336 1.60 25 53.4 84.79 8.24 7.17 −12.99 417 101 F16Ti—30Al Ar 1 0.5 396 1.26 23 54.7 84 8.55 7.34 −14.15 416 94 F17 Ti—30AlAr 1 1.1 458 2.4 54 37.0 82.42 8.79 7.94 −9.67 401 93 F18 Ti50Al Ar 10.4 0.4 1.06 25 49.5 86.72 7.93 6.05 −23.71 285 105 F19 Ti—50Al Ar 1 0.5396 1.26 35 47.4 83.3 8.26 7.01 −15.13 441 100 F20 Ti—90Al Ar 1 0.43 4521.00 28 42.0 84.72 8.08 5.83 −27.85 406 100 F21 Ti—90Al Ar 1 0.6 0.61.22 39 30.4 44.85 7.96 ∞ — 405 103 F22 Ti—90Al Ar 1 0.6 486 1.23 4230.8 44.3 8.27 ∞ — 433 99 FC3 — — 0 0 0 0 0 83.7 84.14 7.66 7.56 −1.31445 107 FC4 — — 0 0 0 0 0 83.3 85.03 8.64 8.43 −2.43 410 102 FC5 — — 0 00 0 0 83.1 85.17 7.94 7.66 −3.53 431 105

Table J shows the deposition parameters for oxides, nitrides, and metalcoatings for a target having an alloy composition of titanium with 75atomic weight aluminum. The results of Table J are shown in FIGS. 17 and18 discussed below. TABLE J Measured XRF Wt % Sample Target ILS CoaterSettings Thickness (ug/cm²) Al No. Alloy KW Pass Volts Amps ILS % T Gas(Å) Al Ti Al J1 Ti—75Al 4.0 5 339 11.6 88.6 80%O2-Ar 114 .80 .58 58.0 J2Ti—75Al 4.0 30 372 10.73 84.6 80%O2-Ar 663 5.26 3.88 57.5 J3 Ti—75Al 3.03 480 6.26 85.0 100%N2 173 1.66 1.16 58.9 J4 Ti—75Al 3.0 20 480 6.2673.2 100%N2 898 11.60 8.32 58.2 J5 Ti—75Al 3.0 1 544 5.51 13.9 Ar 2023.34 2.37 58.5 J6 Ti—75Al 3.0 5 549 5.47 0.0 Ar 1064 17.9 13.0 57.9

Example 8 Comparison of Coating Removal Times for Various Ti—Al Coatings

The target compositions of Table H above were applied to a 2.3 mm thickfloat glass samples and then the removal time of the coating wasmeasured using a conventional Cleveland Condensation Test (CCC)procedure. Multiple sample coupons were cut out of a coated glass sheet.For each sample tested, using the CCC procedure, a neighboring sample(control) was first measured using XRF to determine the number ofmicrograms per square centimeter of the coating. The samples to betested were then placed in the CCC device and removed after set periodsof time (see FIG. 17). A section of the test sample was then measuredusing XRF to determine the amount of coating remaining, which wascalculated by dividing the measured XRF of the sample versus the XRF ofthe control.

FIG. 17 shows the percent coating removed versus time for pure titaniumand aluminum coatings as well as titanium and aluminum coatings having10, 30, 50, 75, and 90 atomic percent aluminum. The samples weresputtered in the manner described in Tables C. D, and J. The coatingthicknesses are shown in Table K below. TABLE K Calculated XRF Wt %Sample Target ILS Coater Settings Thickness (ug/cm²) Al No. Alloy KWPass Volts Amps ILS % T Gas (Å) Al Ti Al K1 Ti 3.00 6 541 5.54 33.8100%N2 253 0.00 7.98  0.0% K2 Ti10Al 2.83 6 577 4.90 37.8 100%N2 2450.40 7.24 5.24% K3 Ti—30Al 2.61 5 646 4.03 46.4 100%N2 223 1.06 5.1317.1% K4 Ti—50Al 2.84 4 560 5.06 59.2 100%N2 196 1.65 3.38 32.8% K5Ti—75Al 3.00 6 499 6.01 76.7 100%N2 197 2.54 1.78 58.8% K6 Ti—90Al 3.055 380 7.90 83.8 100%N2 238 3.69 0.71 83.9% K7 Al 2.74 5 351 7.82 87.3100%N2 186 3.39 0.00  100% K8 Ti 2.96 28 494 5.99 77.6 80%O2-Ar 286 0.005.71  0.0% K9 Ti10Al 2.96 25 500 5.89 81.8 80%O2-Ar 279 0.22 5.05 4.17%K10 Ti—30Al 2.93 28 454 6.45 83.5 80%O2-Ar 318 0.85 4.89 14.8% K11Al50Ti 2.95 20 428 6.90 87.5 80%O2-Ar 238 1.07 2.63 28.9% K12 Ti—75Al3.00 16 354 8.48 88.1 80%O2-Ar 210 1.69 1.26 57.3% K13 Ti90Al 2.88 17322 8.89 88.9 80%O2-Ar 270 2.57 0.66 79.6% K14 Al 2.94 24 305 9.63 88.980%O2-Ar 288 3.13 0.00  100%

Generally, titanium coatings survive longer than aluminum coatings in aCleveland Condensation Test. Therefore, one would anticipate that addingaluminum to a titanium coating would degrade the titanium coating.However, surprisingly, it was discovered that at a ratio of about 50atomic percent aluminum, the titanium and aluminum coating showedsurprisingly better results (i.e., it took longer to remove thecoating).

FIG. 18 shows the time until about 80% of the coating was removed versusthe atomic percent aluminum in the coating. The left of the graphrepresents pure titanium and the right of the graph represents purealuminum. One would anticipate adding aluminum to titanium wouldseverely degrade the ability of the coating to resist mechanical and/orchemical attack. However, FIG. 18 surprisingly shows that rather thandegrading the titanium, the presence of aluminum in the range of about10 to 75 atomic percent actually improves the coating performance, i.e.,it takes longer to remove the coating. It would appear that this effectis most pronounced in the range of about 40 to 60 atomic percentaluminum, with a peak at about 50 atomic percent aluminum.

FIG. 19 is similar to FIG. 17 but shows the results for the nitridecoatings of Table K. Again, a titanium and aluminum nitride coating with50 atomic percent aluminum shows surprisingly unexpected results.

FIG. 20 shows the reactive index (n) and extinction coefficient (k) fortitanium and aluminum-containing coatings deposited in atmospheres ofpure nitrogen or 80% oxygen with the balance argon. From FIG. 20, anoxide coating of titanium and aluminum provides a lower refractive indexthan a nitride coating in the range of about 0 to 60 atomic percentaluminum. Also, the use of titanium and aluminum-containing coatings,e.g., oxides, oxynitrides, nitrides, or metals, in a coating stackprovide a layer that can provide a range of indices of refraction and/orextinction coefficients. By varying the extinction coefficient, one canvary absorption in the coating. The coating of the invention provides arange of refractive indices. As shown in FIG. 19, above 75 atomicpercent Al there is little or no absorption for titanium nitride andthis material has a high refractive index. At 50 atomic percent Al,there is a mid-range extinction coefficient and a high index ofrefraction. One can envision using combinations of the titanium andaluminum material of the invention as oxides, nitrides, oxynitrides, ormetals to produce a wide variety of high index and low index materials.A lower index of refraction permits a thicker optical layer and at thesame time provides enhanced corrosion resistance. One can provide abetter index match to vinyl materials, such as PVB. Higher absorptionlayers provide lower transmittance with functionality, e.g., a lowershading coefficient. The higher absorbing materials contain amounts oftitanium nitride, which are shown in the corrosion data above to be verydurable. Such coatings could be used as first or second surface coatingson window, automotive, or decorative glazings, just to name a few.

The above examples illustrate the present invention which relates tousing titanium and aluminum-silicon, titanium andaluminum-silicon-transition metal and titanium and aluminum-transitionmetal cathode targets sputtered in pure nitrogen, in nitrogen-oxygenmixtures ranging up to 40 percent oxygen, and in argon-oxygen mixturescomprising up to 50 percent oxygen. Based on the data illustrated in thefigures, a single titanium and aluminum-alloy cathode target containinga given weight percentage of silicon, silicon-transition metal ortransition metal can be used for stable sputtering of a range of filmcompositions including oxides, nitrides and oxynitrides with varyingabsorption at high sputtering rates.

It should be appreciated that all of the protective coatings discussedabove can be used within a low emissivity coating, such as but notlimited to those discussed earlier and illustrated in FIG. 1. Moreparticularly, the Ti—Al and Ti—Al—Si oxides, nitrides and oxynitridesand combinations thereof, can be used as dielectric layers like thelayers of ZnSn Oxide or Zn Oxide (layers 44, 50 and 56), and theprotective overcoat in FIG. 1 (layer 16).

It should also be appreciated that the Ti—Al and Ti—Al—Si metal or alloycoatings can be used as primer layers as shown in FIG. 1 (layers 54 and48) over the silver layers. The coatings of Ti—Al and Ti—Al—Si metal oralloy coatings can also be used as the protective overcoat layer asdescribed above and shown in FIG. 1 (layer 16). The metal or alloycoating can be subsequently oxidized to form a metal or alloy oxidecoating during high temperature processing of glass, such as temperingor bending.

It should be further appreciated that all of the above protectivecoatings as described above, when incorporated in or over a lowemissivity coating, e.g., as described above and shown in FIG. 1, can beprocessed at high temperatures, such as tempering and bending of clearfloat glass.

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Accordingly, theparticular embodiments described in detail herein are illustrative onlyand are not limiting to the scope of the invention, which is to be giventhe full breadth of the appended claims and any and all equivalentsthereof.

1-6. (canceled)
 7. A method for depositing coatings comprising titaniumand aluminum, comprising: a. maintaining a substrate in an evacuatedchamber; b. maintaining an atmosphere comprising a gas selected from thegroup consisting of inert gas, nitrogen, oxygen, and mixtures thereof;and c. sputtering an elongated cathode target comprising 1 to 99 weightpercent titanium and 1 to 99 weight percent aluminum, to deposit atitanium and aluminum containing coating on a surface of the substrate.8. The method according to claim 7, wherein the substrate is a visiblelight transmitting substrate.
 9. The method according to claim 7,wherein the substrate is glass or plastic.
 10. The method according toclaim 9, wherein the atmosphere comprises at least one of an inert gas,oxygen, nitrogen, and combinations thereof, and the cathode targetfurther comprises silicon, and the sputtering comprises sputtering acoating that is up to 40 weight percent silicon.
 11. The methodaccording to claim 7, wherein the target comprises 20 to 70 weightpercent aluminum and 30 to 80 weight percent titanium.
 12. The methodaccording to claim 11, wherein the target comprises 5 to 20 weightpercent of another metal containing material.
 13. The method accordingto claim 11, wherein the target comprises 5 to 20 weight percent ofsilicon.
 14. The method according to claim 7, wherein the atmospherecomprises nitrogen, and the coating comprises materials selected fromtitanium, aluminum, titanium-nitride, aluminum-nitride,(titanium-aluminum)nitride, and combinations thereof.
 15. The methodaccording to claim 7, wherein the atmosphere comprises nitrogen andoxygen, and the coating comprises materials selected from titanium,aluminum, titanium oxide, aluminum oxide, (titanium-aluminum)oxide,titanium nitride, aluminum nitride, (titanium-aluminum)nitride, titaniumoxynitride, aluminum oxynitride, (titanium-aluminum) oxynitride, andcombinations thereof.
 16. The method according to claim 7, wherein theatmosphere comprises oxygen and inert gas, and the coating comprisesmaterials selected from titanium, aluminum, titanium oxide, aluminumoxide, (titanium-aluminum)oxide, and combinations thereof.
 17. Themethod according to claim 11, wherein the atmosphere consistsessentially of inert gas and the coating consists essentially oftitanium and aluminum.
 18. The method according to claim 11, wherein theatmosphere comprises oxygen and the coating comprises titanium oxide andaluminum-oxide.
 19. The method according to claim 11, wherein theatmosphere comprises oxygen and nitrogen and the coating comprisestitanium and aluminum-silicon-transition metal oxynitride. 20-34.(canceled)